unity desktop vs unity web player

will every game created in unity run on unity web player too? i mean everything that mono support and unity framework support can work on unity web player? if not what are limitations?

There are security restrictions imposed when running in a webplayer, so, for example, you cannot use System.IO to access the hard drive, and you cannot access remote websites without permission. A long list of Mono classes is shown here:

http://docs.unity3d.com/Documentation/ScriptReference/MonoCompatibility.html

and the security sand box is here:

http://docs.unity3d.com/Documentation/Manual/SecuritySandbox.html